Vacuum pump for use in the automotive sector

ABSTRACT

A vacuum pump for use in the automotive sector includes a rotor element fixed on a rotor shaft and arranged in a rotor housing, an electric drive arranged in a motor housing, a housing wall comprising at least one passage opening, and a bearing device. The rotor housing comprises at least one inlet and at least one outlet. The electric drive directly or indirectly drives the rotor shaft. The housing wall interconnects the rotor housing and the motor housing so as to form a housing assembly. The at least one passage opening fluidically connects the rotor housing and the motor housing. The bearing device supports the rotor shaft in the housing wall.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2011/061628, filed on Jul. 8, 2011. The International Application was published in German on Jan. 17, 2013 as WO 2013/007278 A1 under PCT Article 21(2).

FIELD

The present invention relates to a vacuum pump for use in the automotive sector, comprising a rotor element that is fixed on a rotor shaft and arranged in a rotor housing, and an electric drive body which directly or indirectly drives the rotor shaft and is arranged in a motor housing, the rotor housing and the motor housing being interconnected by a housing wall and forming a housing assembly, the rotor shaft being supported in the housing wall by a bearing device, the rotor housing having at least one inlet and at least one outlet.

BACKGROUND

Various power-consuming devices in the automotive sector, such as, for example, brake systems, are based on underpressure control. In conventional vehicles, the underpressure required for this purpose is in most cases provided either directly by suction tube connectors on gasoline engines or by mechanical underpressure pumps on diesel engines. Especially in hybrid and electric vehicles, use is made of electric underpressure pumps and/or electric vacuum pumps to provide an underpressure supply which is independent from the internal combustion engine. It is further known from practice that the motor for the electric drive of the vacuum pump and the rotor generating the underpressure can be accommodated in a housing assembly. If allowed for by the constructional space, the rotor housing in the longitudinal direction joins the motor housing so that the motor shaft provided with the rotor can be driven directly by the electric drive body. In this arrangement, the motor housing and the rotor housing are connected to each other by a housing wall having the motor shaft extending therethrough. The rotor shaft is supported in the housing wall by a bearing device. Due to the underpressure that is to be built up in the rotor housing, the bearing device is subjected to extremely high stress, with the consequence, for example, that lubricants are sucked into the rotor chamber and a correct bearing support is rendered impossible. In practice, a well-aimed leakage geometry is installed as a remedy which has the effect that air is guided from the outlet to the shaft center so that the stress on the bearing device due to a pressure difference in the motor and rotor housings is kept to a minimum. This approach results in a high technical expenditure in the manufacture of the rotor housing, while the desired leakage also reduces the efficiency of the vacuum pump.

SUMMARY

An aspect of the present invention is to provide a vacuum pump for use in the automotive sector which avoids the above-described disadvantages.

In an embodiment, the present invention provides a vacuum pump for use in the automotive sector which includes a rotor element fixed on a rotor shaft and arranged in a rotor housing. The rotor housing is configured to comprise at least one inlet and at least one outlet. An electric drive is arranged in a motor housing. The electric drive is configured to directly or indirectly drive the rotor shaft. A housing wall comprises at least one passage opening. The housing wall is configured to interconnect the rotor housing and the motor housing so as to form a housing assembly. The at least one passage opening is configured to fluidically connect the rotor housing and the motor housing. A bearing device is configured to support the rotor shaft in the housing wall. A simple and cost-effective pressure equalization is thereby realized between the motor housing and the rotor housing which provides a safe and, with regard to operating life, a durable functioning.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows a sectional view of a vacuum pump according to the present invention; and

FIG. 2 shows a perspective view of a motor housing of the vacuum pump of FIG. 1.

DETAILED DESCRIPTION

In an embodiment of the vacuum pump according to the present invention, the at least one passage opening can, for example, be provided in the area of the bearing device.

The volumetric efficiency of the vacuum pump is increased by sealing the housing assembly in an air-tight manner. Of particular use as a bearing device is an easy to produce and easily mountable rolling bearing, and which, because of the special design of the housing wall with at least one passage opening, is no longer subjected to the high pressure difference which would lead to a grease loss of the rolling bearing. A thrust washer for the rotor element can be provided between the housing wall and a second cylinder wall portion.

An exemplary embodiment of the present invention is illustrated in the drawings and will be described hereunder.

FIG. 1 shows an electrical vacuum pump 2 comprising a housing assembly 4. Housing assembly 4 substantially consists of a motor housing 6 and a rotor housing 8. Within motor housing 6, a per se known electric motor 10 with schematically outlined control electronics 12 is provided. In the shown embodiment, electric motor 10 directly acts on a rotor shaft 14. Rotor shaft 14 can also be provided as a multi-part design or a drive shaft of electric motor 10 can also be connected to rotor shaft 14 via a coupling.

On its end facing away from rotor housing 8, motor housing 6 comprises a cover element 16 on which the control unit 12 for the electric motor 10 is arranged and which comprises a first rolling bearing 18 for support of rotor shaft 14. It should be evident, however, that the electric motor 10 can also be designed as a conventional, mechanically commutated motor. On the opposite end, a housing wall 20 is provided which together with the cover element 16 and a cylinder wall portion 22 seals the motor housing 6 in an air-tight manner. The housing wall 20 comprises outwardly directed fastening flanges 24 for fastening the vacuum pump in the motor compartment. Housing wall 20 further forms a part of rotor housing 8 joining the motor housing 6 in the longitudinal direction and is likewise sealed in an air-tight manner by the housing wall 20. In the shown embodiment, housing wall 20 is thus both a part of motor housing 6 and a part of rotor housing 8. Rotor housing 8 also comprises a second cover element 26 and a second cylinder wall portion 28. A thrust washer 21, made of stainless steel, for a rotor element 32 is provided between the housing wall 20 and the second cylinder wall portion 28. By means of through-bolts 30 extending through the second cylinder wall portion 28, the second cover element 26 is screwed to housing wall 20. Rotor housing 8 is also sealed in a fluid-tight fashion. Rotor housing 8 further comprises, in a known manner, an inlet and an outlet (not shown in the drawings). Rotor shaft 14 comprises rotor element 32 which in the present case comprises a plurality of displaceably arranged vane elements so that, in accordance therewith, the vacuum pump is formed as a vane cell pump. The rotor element 32 cooperates in a known manner with the second cylinder housing portion 28 and accordingly serves to build up an underpressure. A second rolling bearing 34 is arranged in housing wall 20 in which, in turn, is supported rotor shaft 14 and through which rotor shaft 14 extends into rotor housing 8.

Housing wall 20 is further formed with three passage openings 36 arranged directly in the area of second rolling bearing 34. In this manner, a fluidic connection is realized between the rotor housing 8 and the motor housing 6 so that, in the area of the rolling bearing assembly 34, no pressure difference damaging to the roller bearing 34 will exist.

FIG. 2 shows the motor housing 6 in perspective view. Clearly visible is the housing wall 20 with the flange elements 24 via which the vacuum pump can be attached in the motor compartment of the automobile. Rotor shaft 14 is supported in rolling bearing 34 and extends through housing wall 20 into the rotor chamber (not specifically shown) of rotor housing 8. Clearly to be seen are also the passage openings 36 which provide the pressure equalization in the area of rolling bearing 34.

It should be evident that the present invention is not restricted to the realization as a vane cell pump with a plurality of vanes and is also applicable, for example, to a single-vane vacuum pump. Reference should also be had to the appended claims. 

What is claimed is: 1-5. (canceled)
 6. A vacuum pump for use in the automotive sector, the vacuum pump comprising: a rotor element fixed on a rotor shaft and arranged in a rotor housing, the rotor housing being configured to comprise at least one inlet and at least one outlet; an electric drive arranged in a motor housing, the electric drive being configured to directly or indirectly drive the rotor shaft; a housing wall comprising at least one passage opening, the housing wall being configured to interconnect the rotor housing and the motor housing so as to form a housing assembly, the at least one passage opening being configured to fluidically connect the rotor housing and the motor housing; and a bearing device configured to support the rotor shaft in the housing wall.
 7. The vacuum pump as recited in claim 6, wherein the at least one passage opening is provided in an area of the bearing device.
 8. The vacuum pump as recited in claim 6, wherein the housing assembly is sealed so as to be air-tight.
 9. The vacuum pump as recited in claims 6, wherein the bearing device is a rolling bearing.
 10. The vacuum pump as recited in claim 6, further comprising a second cylinder wall portion, wherein the rotor element further comprises a thrust washer arranged between the housing wall and the second cylinder wall portion. 